Vibration under heavy load

[jwr_20]

Hello,<br /><br />I have a 1984 75hp Merc, serial 6503156. While I was out earlier today, I had a few friends in the boat with me, which is the heaviest load I have ever taken in this boat. We were crusing through fairly rough water on Lake Ontario. There was a lot of weight in the bow, but the boat still planed fairly evenly. The motor seemed to run normal for the conditions present for the first while. Then I noticed that it seemed to lose power, and so I gave it a bit more throttle, the rpm's went up, but it vibrated rather than increased in speed, as if the prop was tangled in weeds. After I got back to the dock, I unloaded the boat, and went out for a solo run. It seemed to run perfectly. Could there be a problem with the motor? I am thinking it is just air getting drawn under by the prop.<br /><br />Any ideas, or am I just paranoid? <br />Thanks!

 

[Bob H.]

Re: Vibration under heavy load

Sounds like you may have overloaded the boat and the prop hub is now hurt, or the engine temp was getting hot - alarm work? The hub is subject to failure due to age, you don't always have to hit something.

 

[jwr_20]

Re: Vibration under heavy load

Thanks for the reply!<br /><br />This engine doesn't have a temperature alarm, but the water pump is working perfectly. This motor is getting old, and the prop was actually from an even older motor from around 1977, although I'm not sure if that's the age of the prop or the moter itself.<br /><br />Thanks again for the help!